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Slow hot water heating or is it?

  • 15-10-2013 12:35pm
    #1
    Scuba_Scoper
    Closed Accounts Posts: 183 ✭✭


    Hi - hoping I can tap into the collective on this.

    TLDR; is an increase in water temp of 2-3 deg centigrade per 5 minutes in a hot water copper cylinder normal from oil fired heating?

    Full Version.
    Hot water seemed to be very slow in heating up since the summer. We had a blown immersion replaced early on in the summer and had been using this satisfactorily for the last few months - no issues with this.

    Now that winter is coming, we are back to the oil fired heating and have noticed that the hot water is very slow at heating. Maybe we are just now used to the immersion heating the sink setting.

    So, I nerded out over the last few days, starting at with zero hot water in the tank - starting the oil heating and measuring the hot water temperature every 5 minutes for an hour (I said I nerded out, yeah :-)

    What I found was that the return valve from the cylinder (only 1 zone for both hot water and heating) was nearly completely closed. I opened it 1/4 turn, let the heating settle and measured..... boring details but eventualy, I think I got the right biting point as now the hot water is increasing at approx 2-3 degrees C every 5 minutes.

    Starting from an empty, of hot water cylinder, it takes nearly an hour to go from 17 deg c to 43 deg c. Hot but not very hot. Compared to the Immersion heater which goes to 50 deg c in about 25 minutes.

    What I was hoping someone could tell me is; does all this sound right ? It probably makes no difference when the heating is on all evening. Its just the early morning water heating that I am trying to account for and trying to get my heating system to be more efficient.

    Thanks


Comments

  • #2
    John T Carroll
    Closed Accounts Posts: 757 ✭✭✭John T Carroll


    Scuba_Scoper wrote: »
    Hi - hoping I can tap into the collective on this.

    TLDR; is an increase in water temp of 2-3 deg centigrade per 5 minutes in a hot water copper cylinder normal from oil fired heating?

    Full Version.
    Hot water seemed to be very slow in heating up since the summer. We had a blown immersion replaced early on in the summer and had been using this satisfactorily for the last few months - no issues with this.

    Now that winter is coming, we are back to the oil fired heating and have noticed that the hot water is very slow at heating. Maybe we are just now used to the immersion heating the sink setting.

    So, I nerded out over the last few days, starting at with zero hot water in the tank - starting the oil heating and measuring the hot water temperature every 5 minutes for an hour (I said I nerded out, yeah :-)

    What I found was that the return valve from the cylinder (only 1 zone for both hot water and heating) was nearly completely closed. I opened it 1/4 turn, let the heating settle and measured..... boring details but eventualy, I think I got the right biting point as now the hot water is increasing at approx 2-3 degrees C every 5 minutes.

    Starting from an empty, of hot water cylinder, it takes nearly an hour to go from 17 deg c to 43 deg c. Hot but not very hot. Compared to the Immersion heater which goes to 50 deg c in about 25 minutes.

    What I was hoping someone could tell me is; does all this sound right ? It probably makes no difference when the heating is on all evening. Its just the early morning water heating that I am trying to account for and trying to get my heating system to be more efficient.

    Thanks
    If the water is only reaching 43C then maybe you should check the Boiler thermostat, one relatively easy way to do this is in the evening/night when there is no hot water usage, ensure that the Boiler is firing continuously (On/Off) by turning up the room thermostat, if fitted. The maximum hot water cylinder temperature reached is the mean of the Boiler circulating water.
    I know that my boiler settings are a measured 70C/60c (mean of 65C) and my hot water cylinder reaches a max of 64C with no usage. my cylinder temperature rise is similar to yours ie about 2.5C/5 mins. I have an (oil fired) coil of 0.62 M2 heating 105 Litrs of a 150 Litre hot water cylinder. You might also consider checking the circulating pump settings, normally there are three speed settings, if your speed setting is on 2 then change it to 3., you could then open up the return valve by say another 1/4 turn....open it as much as you can without starving off any of the radiators.
    Re your immersion: you say that it heats the water from 17c to 50C in 25 minutes, if one assumes a 3 KW element, then by calculation, it is probably only heating approx 35 Litres of water. John


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